bone density and muscle strength appear to be more related to each other. Examining the association between muscle strength and bone health is very important in recognizing risk factors for lower extremity muscle weakness.

Dual Energy X-ray Absorptiometry (DEXA) scan will be used to assess hip bone mineral density (BMD) at femoral head region. Isokinetic PT of hip flexors, extensors, abductors and adductors and knee flexors and extensors will be measured using Biodex System 3 Isokinetic Dynamometer. The measured outcomes will be evaluated at an angular velocity of 60°/sec in a concentric mode of muscle contraction for five successive repetitions. Isokinetic testing will be done at the Isokinetic Laboratory, Faculty of Physical therapy, Cairo University.

Inclusion Criteria:

1. The group of OP (n=33) has femoral BMD T-scores below -2.5 diagnosed by DEXA scan according to the WHO [8] classification of BMD in 2003,
2. The control group has normal BMD T-scores more than -1.

Exclusion Criteria:

1. There was any neurological, musculoskeletal, rheumatologic, respiratory or cardiovascular problem.
2. They were receiving medications that result in bone loss such as corticosteroids,
3. They had vertigo, dizziness, or any vestibular problem,
4. They had hyperthyroidism or hyperparathyroidism. 6- They actively participate in sports activities,
5. They underwent previous surgery (e.g; joint replacement) or history of fractures of the lower extremity.

Based on a sample size calculation via G Power software, a total of 70 participants will be required to participate in the study taking in consideration 20% drop out. A total 66 elderly women with ages range from 50 to 70 years will be involved in the study